Gas-operated self-loading firearm



C. G. SWEBILIUS GAS-OPERATED SELF-LOADING FIREARM Aprifl 10, 1945.

Filed March 5, 1943 4 Sheets-Sheet l F mm am qm an mm April 1945 1 c. G. S WEBILIUS 4 ,373,204

GAS-OPERATED SELF-LOADING FIREARM 4 Sheeis-Sheet 2 Filed March 5, 1943 Ill 1/0 Ami! 10, 1945- c. e. SWEBILIUS GAS-OPERATED SELF-LOADING FIREARM Filed March 5, 1943 4 Sheets-Sheet 3 vh' /Lm In low/26y;

April 10,: 1945. Q G, SWEBIUUS 2,373,204

' GAS-OPERATED SELF-LOADING FJIREARM Filed March 5, 1945 4 Sheets-Sheet 4 3a @19 1% w 5o Patented Apr. 10, 1945 ,UNITED STATES PATENT OFFICE cas-ornnsgggglmmonnmo Earl G. Sweb'ilius, Hamden, flonn.

Application March '5, 1943, Serial-No. 178,058

11 Claims.

The present invention relates :to improvements in gas-operated self-loading firearms, i. -e., firearms in which the energy developed by the .discharge :ofone cartridge effects the extraction and ejection of the said cartridge preparatory to the insertionof a fresh cartridge. More particularly, the present invention relates to means f'fOl operatively interconnecting the piston and breech-bolt of a firearm of the type referred to,

one of the objects of the present invention is to provide a gas-operated self-loading firearm in which superior means is provided for operatively interconnecting the vpiston and the breech-bolt.

Another object of the present invention :is to provide superior means for 'operatlvely intercom necting the piston and breech-bolt of a gas-operated self-loading firearm in such manner that' the said means may be readily disconnected from .the structure to permit inspection, repair and 'replacement.

A further object of the present invention is to provide superior means for operative'ly interconmeeting the breech-bolt and piston of ages-loner- :ated self-loading firearm, which .means .is char-- acterized by reliability and effectiveness of opera- :a'tion, combined with capacity for convenient disassembly.

With the above and other objects in View, as will appear :to those skilled in the art from'the present disclosure, this invention includes all features in the said disclosure which :are novel over the prior art and which are not claimed in any separate application.

in the accompanying drawings, in which certain modes of carrying out the present invention are shown .for illustrative purposes:

Fig. la is a broken view partly in sideelev-ation and partly in vertical central-longitudinal section of the intermediate portion 'of a firearmstructure embodying the present invention;

Fig. lb is a similar view of the portion of the firearm immediately forward of "the portions shown in Fig. la;

Fig. 2 is a transverse sectional view taken on the :line 2-2 of .Fig. lb;

Fig. 3 is a similar view taken on the line 3--3 of :Figb;

Fig. 4.- is a broken longitudinal sectional view taken on the line 4- of Fig. 2;

.Fig. 5 is a broken longitudinal sectional view taken on the line 55 of Fig. 1a;

:Fig. 6 is a transverse sectional view taken on the line G6 of tliig. .16;

Fig. '7 is an inner face view of the faction-slide, detached;

Fig. B is a view in side elevation of the conheating-link, detached;

Fig. 9 is-a view in side elevation .of the cylinderfitting, together with the portion of the barrel adjacent thereto;

Fig. .10 is a perspective view of the piston, detached;v

Fig. 11 is a view corresponding to Fig. 4 but showing the connecting-link in the position which it assumes during its attachment to or detachnent from the piston;

Fig. 12 is a perspective view of the spring-re- .taining unit, detached; and

Fig. i3 is a broken longitudinal sectional view :of the same nature as Fig. 4 butshowing amodlfled construction .of the connecting-link and piston.

The structure .0 Figs. .1 to 12 inclusive The gas-operated self-loading firearm chosen for purposes of illustrating one embodiment of the present invention in the figures referred to, includes .in the main a frame 15, a receiver :IfG, a barrel H, a stock 1'8 and a barrel-cover 19. The firearm also includes a breech-bolt '20, an actionslide 2"l,, 'a connecting-link .22, a reciprocatingpiston 23 and a cylinder-fitting 24.

The stock 18 and barrel-cover i9 above *referred to are preferably formed of wood or other suitable heat-insulating and shock-absorbing material, while the remaining par-ts above *described are preferably formed of 'h igh g-rade steel.

The frame 15 is mainly of plate-like form and is formed on its lower edge with a loop-like trigger-guard 2-5 extending around a trigger 2B which controls the r-firing mechanism of the firearm in anysuitable manner not requiring :detailed description herein.

The frame 1 5 is rigidly secured to the stock 118 in any suitable manner such, ior instance, as by a belt 231, while thersa-id "trame [=5 and receiver 16 are detachably secured together in any suitable manner not requiring detailed description herein, sothatin effect the "two said elements :may :be said to constitute artrame structure. The barrel 1/? is rigidly coupled at its rear end with the "for-- 'wardiend'of the receiver t6, which latter is generall-y :of cylindrical .form exterlorfly and is provided in its ii-iiver i'or with an axial passage 28 in which the breech-bolt 20 tooth reciprocates and oscillates.v The rear end :of the passage :28 just referred to is closed by a standing-breech 29 -forming part of the upper rear portion of .irame 15.

length thereof, is an ejection-opening 33 through which the cases of fired cartridgesmay be ejected in any convenient manner not requiring detailed description herein. 7

The outer end of the lug 30 of the breech-bolt projects into a cam-recess 34 formed in the inner face of the action-slide 2| and acting on the said lug to both turn the same to unlock and lock the breech-bolt and to reciprocate the said breech-bolt in a manner well understood in the art and broadly similar to the manner in which the breech-bolt of the well-known Garand military rifle is operated.

The inner face of the action-slide 2| is cylindrically contoured to correspond to the exterior contour of the adjacent portion of the receiver l6 upon which the said action-slide reciprocates in a direction lengthwise of the firearm-structure;

The action-slide 2| is preferably formed of two major parts for purposes of economy, namely, a sheet-metal shell 35 of circular arc form in cross section and a relatively-heavy body 35'brazed or otherwise rigidly united to the outer surface of the said shell 35. Adjacent its rear end and hence about midway the length of the actionslide 2|, the body 36 of the said action-slide is provided with an outwardly-projecting operating-handle 3'! by means of which the said action- I slide and hence the breech-bolt 20 may be manually operated when desired.

About midway of its length, the action-slide 2| is formed with a downwardly-and-inwardlyopening recess 38 which receives a coupling-lug 39 projecting inwardly from the rear end of the connecting-link 22 before referred to. Adjacent and intersecting its recess 38', the action-slide 2| is formed with a horizontal slot 40 which also intersects the exterior periphery of the said action-slide both to the front and to the rear of the operating-handle 31, I v

Mounted about midway'of its length in the horizontal slot 40 in the action-slide 2| is a couplinglever 4| swinging upon a, pivot-pin 42 mounted vertically in the base portion of the operatinghandle 31 of the action-slide 2|, as is clearly shown in Figs. 5, 6 and 7. At its forward end, the coupling-lever 4| is provided with a substantially-semicircular coupling-nose 43 normally entered into a coupling-recess 44 formed in the outer face of the coupling-lug 39 ofthe connecting-link 22. The rear end of thecoupling-lever 4| is broadened laterally to provide a convenient flnger-piece and is located immediately to the .rear of the operatingahandle 31 of the actionslide 2|. A helical spring 45 is interposed between the rear end of the coupling-lever 4| and the rear end of the, action-slide 2| in position to exert a yielding force in a direction to turn the said coupling-lever 4| in a counterclockwise direction as viewed in Fig. ,5 andhence to yieldingly maintain its coupling-nose 43 in the coupling-recess of, the action-slide 2|.- 'The coupling-lever 4| thus serves to releasably holdthe rear end of the connecting-link 22 in coupled relationship with respect to the action-slide 2|.

For the purpose of guiding the reciprocating movement of the action-slide 2| on the receiver IS, the said action-slide has the respective opposite side-edges of its sheet-metal shell 35 bent substantially radially inwardly to provide two parallel longitudinal guide-flanges 46 and 4? respectively. In line with each of the guide-flanges 45 and 41 just referred to, the receiver I6 is formed on its outer surface with one of two parallel guide-grooves 48 and 49 respectively receiving with a sliding fit the guide-flanges 46 and 41, as is especially well shown in Fig. 6. At their respective forward ends, the guide-grooves 48 and 49 just referred to intersect the forward end of the receiver l5, so that the action-slide 2| may be conveniently removed and installed.

. Returning now to the cylinder-fitting 24 before referred to, it will be noted by reference to Figs. 1b, 3 and 9 in particular, thatthe said fitting includes a body-portion 50, the upper portion of which is formed with a cylindrically-com toured passage 5| extending longitudinally therethrough from end to end and snugly fitting a similarly-contoured portion52 of the barrel 11. The body-portion 50 of the cylinder-fitting 24 also extends below the adjacent portion of the barrel II and in its lower portion is provided with a longitudinal rearwardly-opening piston-chamber 53 having its forward end sealed by a closurescrew' 54. Vertically intermediate its cylindrical passage 5| and the piston-chamber 53, the bodyportion 50 has an anchoring-pin 55 extending transversely therethrough and through the lower part of the portion 52 of the barrel IT.

The cylinder-fitting 24 also includes a tubular extension 56 rigid with and projecting rearwardly from the lower part of the body-portion 50 and having an internal bore 51 arranged coaxially with respect to the piston-chamber 53. Adjacent the forward end of the connecting-link 22, the cylinder-fitting 24 is formed with a longitudinal clearance-slot 58 extending rearwardly from the body-portion 50 to a point closely approaching the rear end of the extension 56, as is clearly shown in Fig. 9.

For the purpose of conducting gas under pressure into the piston-chamber 53 of the cylinderfitting 24 from the bore 59 of the barrel ll, the said barrel is formed with a vertical gas-passage 60 leading downwardly from the said bore 59 to the underside of the portion 52, The lower end of the gas-passage 60 just referred to communicates with the upper end of a gas-passage 6| formed in the body-portion 50 of the cylinderfitting 24. At its lower end, the gas-passage 5| communicates with the forward portion of the piston-chamber 53 at a point immediately rearwardly of the closure-screw 54.

Reciprocating partly in the piston-chamber 53 and partly in the bore 51 of the cylinder-fitting 24, is the piston 23 before referred to. The forward portion of the said piston 23 is smaller in diameter than its rear portion, and at its extreme forward end is formed with a piston-head 62 having a close sliding fit in the piston-chamber 53. lhe rear portion of the piston 23 is sized to have a smooth sliding fit with respect to the surfaces of the bore 51 in the cylinder-fitting 24. The rear portion of the, piston 23 is also provided with a rearwardly-opening cylindrically-contoured socket 64 into which extends the forward ,en'dof a helical breech-closing spring 65.

front wall it of the socket 64 in the piston 23 and extending rearwardly, is a clearance-slot 61 located circumferentially in line with the longitudinal clearance-slot '58 in the cylinder-fitting 2d. Extending diagonally downward and inwardly'from the forward end of the coupling-link 22, is an integral front coupling-lug 68 which passes through both the clearance-slot 58 in the cylinder-fitting 2 and through the clearance-slot 61 in the piston 2-3 and'into the socket 64 in the latter, as is especially well shown :in'Figs. 2 and 4. The coupling-lug 68 includes a forwardly-extending coupling-finger 69 having its respective upper and lower edges cylindrically contoured and loosely fitting the forward portion of the socket Ed in the piston '23, as is 'best shown in Fig. '4. The front coupling-lug '58 is also formed with "a short rearwardly-extending locking-finger I10 fitt'in'g within the forward end of the breech-closing spring 555.

As'tnus constructed and arranged, the breech- -c1osing spring 65 thrusts forwardly upon the front coupling-lug 58 of {the connecting-link 22 and serves to yieldingly urge thesaid connectinglink, the piston 23, the action-slide 2i and the breech-bolt 20 into their respective forward pOSitions. By fitting over the locking-finger ll] of the front coupling-lug 5B, the forward end of the breech-closing spring 65 serves to positively restrain the said coupling-lug from being removed radially outwardly from within the socket 64 .in

. the piston 23 until the said spring is first removed in a manner as will be later described herein. Normally, the upper surface of the couplingfinger E9 of the front coupling-lug E8 positively acts to restrain the radial movement referred to and receives on its forward face the thrust from the fro-nt'wall 65 of the socket L64 of the piston '23 when the said piston is moved rearwardly by gas pressure in a manner :as will hereinafter appear.

The rear portion of the breech-closing spring 65 encircles a spring-guiding rod FI I rigidly secured to and extending forwardly from the depending-arm of a substantially-Z-shapedbracket l2 removably mounted against the under face of the receiver it, as is shown in Fig. 1a. 1% its forward end, the bracket 12 is reversely bent to provide an integral upwardly-and-rearwardly-inclined coupling-finger 13 fitting into a similarlyinclined coupling-recess or socket 14 formed in the lower forward corner of the receiver It, as shown in Fig. 1a. Immediately worwardly of the point of its securement to the bracket 1-2,,the rear end of the springguiding rod 1] is formed with an annular collar 75 receiving-on its forward face the rearward thrust of the breech closing spring 65. The tension of the-breech-closing spring '65 normally holds the coupling-finger 13 of the bracket 12 in the coupling-recess 14 of the receiver it.

When the firearm is discharged, gas pressure from the bore 59 of the barrel ll will pass downwardly through the gas-passages B0 and BI into the forward endof the piston-chamber 53. This gas will act on the forward end of the pistonhead 62 of the piston '23 to drive the said piston violently rearwardly. The rearward movement of the piston 23 will b transmitted to the front coupling-lug 58 of the connecting-link 22 by the engagement of the front wall {56 0f the socket 6 1 in the said piston with the forward end of the coupling-finger 59. Thus, the connecting-link 22 will be driven rearwardly, and through the intermediary of its rear coupling-lug 39 and the rear wall of the recess 38 in the action-slid 21, the said action-slide will be also moved rearwardly.

The rearward movement imparted to the 'action-slide 2:1 as above described, will cause the said action-slide to act through the intermediary of :its cam-recess '34 and the luget on the forward :endiof the breech-bolt 20, to turn and rearwardly retire the said breech-bolt and thus effect the extraction and ejection of the just-firedcartridge. The rearward movement of the parts as just above described will be limited by the engagement of the rear face of a stop-finger 76 formed on the connecting-link 22 with the forward face of a collar ll mounted on the barrel ll immediately forwardly of the receiver 16.

The rearward movement of the parts .as above described under the impulse suppliedby gas ,pressure of the just-fired cartridge will occur against the counterurge of the breech-closing spring 65. Normally, all of the parts referred towhich have just completed their respective-rearward move- :ments, will immediately return to their forward positions under the urge of the breech-closing spring '65 immediately following the checking of the rearward movement of the parts as described. This return or forward movement of the parts will cause the breech-bolt to insert a fresh cartridge into the cartridge-chamber of the firearm in a suitable manner well understood in the art, preparatory to another cycle of operation.

Should it be desired to disassemble the firearm,

the barrel-cover 19 may first be removed, following which the stock may be detached from the remainder of the firearm mechanism. The unit comprising the receiver i6 and barrel ll may now be separated from the frame it in any suitable manner, whereupon the exposed parts are .now in condition to have the parts 20, 2i, 22, '23 and other associated parts completely dismounted.

The next convenient step in the dismounting of the firearm parts would be to thrust forward- 1y upon the bracket 12 to disengage its couplin finger '13 from the recess I l, whereupon the said bracket and the rear end of the said springguiding rod .1 i may be swung laterally or down wardly, after which the said parts may be jointly removed from the receiver It in a rearward direction. The breech-closing spring 65 may now be withdrawn rearwardly from the cylinder-fitting 24 and from the interior of the piston 23 to thus unlock the forward end of the connecting-link 22from the said piston.

The rear. end of the coupling-lever ll carried by the action-slide 2| .may now be forced inwardly to disengage the coupling-nose 43 from the coupling-recess '44 in the rear coupling-lug 39 of the connecting-link 22. The rear end of the said connecting-link 22 may now be moved downwardly to remove its rear coupling-lug 39 from the recess 38 in the action-slide 2|. Now by swinging the rear end. of the connecting-link 22 outwardly and then upwardly to bring the said connecting-link into substantially the position in which it is shown in Fig. 11, the front couplinglug 68 may be withdrawn outwardly through the clearance-slot t1 in the piston 23 and through from the action-slide 2| by moving the said breech-bolt to the limit of its rearward movement, to thereby bring the relatively-slender forward end of the breech-bolt into the relatively large-diametered rear portion of the axial passage 28 in the receiver 16. The forward end .of the breech-bolt may now be swung laterally to disengage its lug 38 from the cam-recess 34 in the action-slide 2 l, whereupon, if desired, the actionslide 2| may then be removed from the receiver i6 by sliding the said action-slide forwardly a sufficient distance to cause the rear ends of its guide-flanges 46 and 41 to clear the forward ends, respectively, of the guide-grooves 4B and 49 in the receiver I E.

The restoration of the parts to their assembled positions will be fully apparent from the foregoing description and the accompanying drawings.

The structure of Fig, 13

to the clearance-slot 5'1 before described.

The connecting-link 18 corresponds to the connecting-link 22 before described, save that at its forward end it is provided with a front couplinglug 83 having a dimension lengthwise of the firearm slightly less than the longitudinal dimension of the clearance-slot 82 in the piston 19. The said coupling lug 83 is provided with a forwardlyprojecting coupling-finger 84 normally resting against the front wall 8! of the socket 80 in the piston 19. The said coupling-lug 83 is also formed with a rearwardly-projecting locking-finger 85 fitting within the forward end of the breech-closing spring 65.

As thus constructed, the forward end of the breech-closing spring 65 serves to positively prevent the radial outward movement of the'front coupling-lug 83 of the connecting link 18, even though the said coupling-lug be moved rearwardly relative to the piston 19 sufiiciently to bring the said coupling-lug into radial alignment with the clearance-slot 82 in the said piston.

By first rearwardly removing the breech-cl0sing spring 55, the coupling-lug 83 of the cometing-link '18 may be brought into registry with the clearance-slot 82 in the piston 19, following which the said coupling-lug may be withdrawn radially outwardly through the said clearance-slot to totally free the forward end of the connecting-link 18 from the piston. The remaining parts may be disassembled and reassembled in the same manner as was made clear in connection with the description of the structure of Figs. 1 to 12 in-.

clusive.

The invention may be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

Iclaim: v

1. A gas-operated self-loading firearm-structure including in combination: a frame-structure; a breech-bolt movable in the said framestructure; a barrel projecting forwardly from the said frame-structure; a cylinder located adjacent the said barrel and having a rearwardly-opening piston-chamber communicating with the bore of the said barrel; a hollow piston reciprocating in the piston-chamber of the said cylinder and formed with a lateral opening extending between its hollow interior and its outer periphery; connecting-means operatively interconnecting the said piston and the said breech-bolt, including a link-like connecting-member extending lengthwise of the firearm-structure and having a coupling-portion extending laterally through the lateral opening in and into the hollow interior of the said piston to couple the connecting-member to the said piston; and breech-closing springmeans extending within the hollow piston and thrusting forwardly upon the laterally-extending coupling-portion of the said link-like connectingmember to cause the same to correspondingly thrust the said piston and the said breech-bolt.

2. A gas-operated self-loading firearm-structure including in combination: a frame-structure; a breech-bolt movable in the said framestructure; a barrel projecting forwardly from the said frame-structure; a cylinder located adjacent the said barrel and having a rearwardly-opening piston-chamber communicating with the bore of the said barrel; a piston reciprocating in the piston-chamber of the said cylinder and formed with a rearwardly-opening socket and with 8. lateral passage leading from the said socket intermediate the ends thereof to the outer periphery of the said piston; connecting-means operatively interconnecting the said piston and the said breech-bolt and including a connecting-member extending lengthwise of the firearm-structure and having a coupling-portion extending laterally through the lateral passage and into the socket in the said piston, the said coupling-portion being provided with a coupling-finger extending therefrom in the socket in the said piston in a direction lengthwise thereof beyond the adjacent end of the lateral passage in the piston; and breech-closing spring-means thrusting forwardly upon the laterally-extending coupling-partion of the said connecting-member to cause the same to move the said piston and the said breechbolt in a corresponding direction.

3. A gas-operated self-loading firearm-structure including in combination: a frame-structure; a breech-bolt movable in the said framestructure; a barrel projecting forwardly from the said frame-structure; a cylinder located adjacent the said barrel and having a rearwardly-opening piston-chamber communicating with the bore of the said barrel; a piston reciprocating in the piston-chamber of the said cylinder and formed with a rearwardly-opening socket and with a lateral passage leading from the said socket intermediate the ends thereof to the outer periphery of the said piston; connecting-means operatively interconnectin'g the said piston and the said breech-bolt and including a connecting-member extending lengthwise of the firearm-structure and having a coupling-portion extending laterally through the lateral passage and into the socket in the said piston, the said coupling-portion being provided with a coupling-finger extending forwardly therefrom in the socket in the said piston and beyond the forward end of the lateral passage in the said piston; and breech-closing spring-means thrusting forwardly on the connecting-memberof the said connecting-means to cause the same to forwardly move the said piston and the said breech-bolt.

4. A gas-operated self-loading firearm-structure including in combination: a frame-structure; a breech-bolt movable in the said frame-structure; a barrel projecting forwardly from the said frame-structure; a cylinder located adjacent the said barrel and having a rearwardly-opening piston-chamber communicating with the bore of the said barrel; a piston reciprocating in the pistonchamber of the said cylinder and formed with a rearwardly-opening socketand with a lateral passage leading from the said socket intermediate the ends thereof to the outer periphery of the said piston; connecting-means operatively interconnecting the said piston and the said breech-bolt and including a connecting-member extending lengthwise of the firearm-structure and having a coupling-portion extending laterally through the lateral passage and into the socket in the said piston, the said coupling-portion being provided with a coupling-finger extending forwardly therefrom in the socket in the said piston and beyond the forward end of the lateral passage in the said piston; and breech-closing spring-means extending forwardly into the socket in the said piston and thrusting forwardly upon the rear of the lat orally-extending coupling-portion of the said connecting-member to causes the same to forwardly urge the said piston and the said breechbolt.

5. A gas-operated self-loading firearm-struc- I ture including in combination: a frame-structure; a breech-bolt movable in the said frame-:structure; an action-slide slidable longi d lly n he said frame-structure and operatively connected to the said breech-bolt; a barrel projecting forwardly from the said frame-unit; a cylinder located adjacent the said barrel and having a rearwardly-opening piston-chamber communicating with the bore of the said barrel; a hollow piston reciprocating in the piston-chamber of the said cylinder and formed with a lateral opening extending between its hollow interior and its outer periphery; a connecting-link having a rear-portion detachably connected to the said actionslide and having a coupling-portion adjacent its forward end extending laterally through the lateral opening in and into the hollow interior of the said piston to couple the connecting-link to the said piston; and breech-closing spring-means extending within the hollow piston and'thrusting forwardly upon the laterally-extending coupling-portion of the said connecting-link to cause the latter to correspondingly urge the said action-slide and the said piston.

6. A gas-operated self-loading firearm-structure including in combination: a frame-structure; a breech-bolt movable in the said frame-structure; an action-slide slidable longitudinally on the said frame-structure and operatively connected to the said breech-bolt; a barrel projecting forwardly from the said frame-structure; a cylinder located adjacent the said barrel and having a rearwardly-opening piston-chamber communieating with the bore of the said barrel; a piston reciprocating in the piston-chamber of the said cylinder and formd with a rearwardly-opening socket and with a lateral passage leading from the said socket intermediate the ends thereof to the outer periphery of the said piston; a con necting-link having a rear-portion detachably connected to thesaid action-slide and having a coupling-portion adjacent its forward end extending laterally through the lateral passage and into the socket in the said piston to couple the said connecting-link to the said piston, the said coupling-portion being provided with a couplingfinger extending therefrom in the socket in the said piston in a direction lengthwise thereof beyond the adjacent end of the lateral passage in the piston; and breech-closing spring-means engaging with and forwardly urging upon the laterally-extending coupling-portion of the said connecting-link to cause the latter to correspondingly urge the said action-slide and the said piston.

'7. A gas-operated self-loading firearm-structure includingin combination: a frame-structure; a breech-bolt movable in the said frame-structure; an action-slide slidable longitudinally on the said frame-structure and operatively connected to the said breech-bolt; a barrel projecting forwardly from the said frame-structure; a cylinder located adjacent the said barrel and having a rearwardly-opening piston-chamber cornmunicating with the bore of the said barrel; a piston reciprocating in the piston-chamber of the said cylinder and formed with a rearwardly-opening socket and with a lateral passage leading from the said socket intermediate the ends thereof to the outer periphery of the said piston; a connecting-link having a rear-portion detachably connected to the said action-slide and having a con" pling-portion adjacent its forward end extending laterally through the lateral passage and into the socket in the said piston to couple the said connecting-link to the said piston, the said coupling-portion being provided with a couplingfinger extending forwardly therefrom in the socket in the said piston and beyond'the forward end of the lateral passage in the said piston; and breech-closing spring-means extending forwardly into the socket in the said piston and thrusting forwardly upon the rear of the laterally-extending coupling-portion of the said connecting-link to cause the same to forwardly urge the said piston and the said action-slide.

8. A gas-operated self-loading firearm-structure including in combination: a frame-structure; a breech-bolt movable in the said framestructure; a barrel projecting forwardly from the said frame-structure; a cylinder located adjacent the said barrel and having a rearwardly-opening piston=chamber communicating with the bore of the said barrel; a piston reciprocating in the piston-chamber of the said cylinder and formed with a rearwardly-opening socket and with a lateral passage leading from the said socket intermediate the ends thereof to the outer periphery of the said piston; connecting-means operatively interconnecting the said piston and the said breech-bolt and including a connecting-member extending lengthwise of the firearm-structure and having a coupling-portion extending laterally through the lateral passage in the said piston; and breech-closing spring-means extending forwardly into the open rear end of the socket in the said piston and into interlocking engagement with the laterally-extending coupling-portion of the connecting-member of the said connecting-means.

9. A gas-operated self-loading firearm-structure including in combination: a frame-structure; a breech-bolt movable in the said framestructure; a barrel projecting forwardly from the said frame-structure; a cylinder located adjacent the said barrel and having a rearwardly-opening piston-chamber communicating with the bore of the said. barrel; a piston reciprocating in the piston-chamber of the said cylinder and formed with a rearwardly-opening socket and with a lateral passage leading from the said socket intermediate the ends thereof to the outer periphery of the said piston; connecting-means operatively interconnecting the said piston and the said breech-bolt and including a connecting-member extending lengthwise of the firearm-structure and'having a coupling-portion extending lateral- 1y through the lateral passage in the said piston, the said coupling-portion being provided with a rearwardly extending locking finger; and breech-closing spring-means extending forward- 1y through the open rear of the socket in the said piston and into locking engagement with the locking-finger of the coupling-portion of the said connecting-member.

10. A gas-operated self-loading firearm-structure including in combination: a frame-structure; a breech-bolt movable in the said framestructure; a barrel projecting forwardly from the said frame-structure; a cylinder located adjacent the said barrel and having a rearwardly-opening piston-chamber communicating with the bore of the said barrel; a piston reciprocating in the piston-chamber of the said cylinder and formed with a rearwardly-opening socket and with a lateral passage leading from the said socket intermediate the ends thereof to the outer periphery of the said piston; connecting-means operatively interconnecting the said piston andvthe said breechbolt and including a connecting-member extending lengthwise of the firearm-structure and having a coupling-portion extending laterally through the lateral passage in the said piston, the

ill

said. coupling-portion being provided with a rearwardly-extending locking-finger; and a helical breech-closing spring projecting forwardly into the socket in the said piston and having its for ward portion encircling the locking-finger on the coupling-extension of the said connecting-member.

11. A gas-operated self-loading firearm-structure including in combination: a frame-structure; a breech-bolt movable in the said framestructure; a barrel projecting forwardly from the said frame-structure; a cylinder located adjacent the said barrel and having a rearwardly-opening piston-chamber communicating with the bore of the said barrel; a piston reciprocating in the piston-chamber of the said cylinder and formed with a rearwardly-opening socket and with 2. lateral passage leading from'the said'socket intermediate the ends thereof to the outer periphery of the said piston; connecting-mean operative-' ly interconnecting the said piston and the said breech-bolt and including a connecting-member extending lengthwise of the firearm-structure and having a coupling-portion extending laterally through the lateral passage and into the socket in the said piston, the said coupling-portion being provided with a coupling-finger extending forwardly therefrom in the socket in the said piston beyond the forward end of the lateral passage in the said piston, the said coupling-portion also being provided with a locking-finger extending rearwardly in the socket of the said piston; and breech-closing spring-means projecting forwardly into the socket in the said piston and into looking engagement with the locking-finger of the coupling-portion of the said connecting-member.

CARL G. SWEBILIUS. 

